Transparent window with non-transparent contact surface for a soldering bonding

ABSTRACT

A transparent pane, in particular a glass pane, having at least one electroconducting, non-transparent contact surface placed on one of its surfaces, to connect it by soldering to a connection piece. In the region of the soldering location, the contact surface has at least one cutout via which the soldering filler metal is visible through the pane after the connection piece has been soldered to the contact surface. Such a configuration allows reliable visual verification of the soldering locations, even in cases in which the soldering location is incorporated within a composite glazing panel and has been soldered, if necessary by induction heating.

The invention relates to a transparent pane, in particular a glass pane,having at least one electroconducting, nontransparent contact surfaceplaced on one of its surfaces, in order to connect it by soldering to aconnection piece.

Such panes are known in many constructions. In most applications, thepanes carry, on their surface, electrical functional elements such aselectrically conducting tracks, heating surfaces, or antennas, again inthe form of coatings over the entire surface, which have to be connectedwith at least one contact surface to an external connection piece bysoldering.

Often the contact surfaces (for example, the conducting tracks or,depending on the case, the functional elements themselves) are producedby applying an electrically conducting paste to be baked; sometimes,thin strips of tinned metal foil are also used, these being connected bysoldering to the surface of the pane, which is pretinned whereappropriate. In all these cases, a connection piece is applied to thecontact surface via the free side and is then soldered.

Many methods of producing composite glazing panels are also known thatincorporate electrical functional elements between their rigid panes andare provided, near the edge of the composite glazing panel, withelectrical connection pieces to be soldered of the type indicated at thebeginning, and of course connection pieces, if possible flat pieces, areused in this case, these having, for example, the structure described indocument DE-C2 19 536 131. It has also already been proposed (DE-C1 19829 151) to supply the heat needed for the soft soldering by inductionor laser beam only after a precomposite has been produced. The term“soft soldering” is understood to mean the use of a filler metal forsoldering that has a low melting point, one that does not exceed atemperature of 450° C.

As a general rule, the connection pieces to be soldered or the solderinglocations themselves are optically masked by means of opaque coloredlayers. In most standard cases of use as a vehicle window pane, thepanes are almost always provided with a peripheral border band in theform of a frame made of a black screen-printing paste that is perfectlysuitable for also masking the regions of electrical connections. Saidcollector rails or actual contact surfaces are also not transparentbecause they are made of a screen-printing paste with a high silvercontent or, as was indicated, in the form of bands of metal foil. On thepassenger compartment side of the vehicle, the border regions of thepanes and the mounting flanges on the body that bear them are usuallycovered and masked by interior furnishing elements.

In general, for transparent panes provided with contact surfaces, inparticular for the soldering places located on the inside of a compositeglazing panel, which are heated only after this composite has beenmanufactured, the problem arises of being able to reliably check theresult of the soldering through the pane.

Although document EP-B1-281 351 describes one particular illustrativeexample of such soldering locations, in which a framed contact surfaceis produced on an opaque coating of the surface of a glass pane using aspecial screen-printing pattern on the structure of which the liquidsoldering filler metal can adhere better, visual inspection of thesesoldering places is possible only from the free side of the pane;because of the opaque coating, the rear side of the contact surface isnot visible through the actual pane.

The problem at the basis of the invention consists in proposing asolution to the abovementioned problem.

According to the invention, this problem is solved in that, in theregion of the soldering location, the contact surface has at least onecutout via which the soldering filler metal is visible through the paneafter the connection piece has been soldered to the contact surface. Thefeatures of the dependent claims provide this subject matter withadvantageous developments.

Owing to the fact that at least one observation window is formed in theactual contact surface, which window remains visible through thetransparent pane provided with the contact surface after the locationsof the connection pieces have been soldered, it is possible to see, bysimple visual verification, whether the soldering filler metal hasmelted and to what extent. Overall, the amount of soldering filler metaland the soldering location will be determined so that, in the event ofcorrect soldering, part of the soldering filler metal flows so as to beoptically visible in said observation window, or, depending on the case,so as to make the modification resulting from the melting of the surfacestructure of the soldering filler metal visible. In this way, thesoldering filler metal after soldering being spread out over the contactsurface and possibly in the cutout or cutouts, the visual inspection mayeven be, where appropriate, automated by means of digital cameras. Thepane itself remains unaffected.

A cutout, for example, a hole 3 to 5 mm in diameter in the contactsurface, is sufficient to leave the tinned surface of the connectionpiece visible. The trained eye of a verifier or a suitable opticalmonitoring device detects whether complete soldering has taken place. Itis obvious that, should the need arise, several of these cutouts may beprovided beside one another and may be arranged where appropriate in apredetermined pattern.

If the contact surface is applied by screen printing, it will beadvantageous to provide, in the screen-printing screen, at the place ofthe location or locations in question, an appropriate mask that preventsapplication of the screen-printing paste in the region of the cutout. Ifthe contact surface is formed by a band of metal foil, the cutout may becut out or stamped by suitable tools at the intended point.

For reliable soldering, it is possible to provide, on the one hand,several small deposits of soldering filler metal (in the form of dropsor in the form of a thin layer) on the corresponding contact surface ofthe connection part to be soldered. After the soldering operation, acheck may be made by observing directly through said cutout made in thesoldering region of the contact surface whether these deposits ofsoldering filler metal have melted and coalesced.

If, in order to minimize the total thickness of the connection region(in particular when it has to be incorporated into a composite glazingpanel), regular pretinning of the corresponding contact surface (theconnection piece) with a thin layer of soldering filler metal ispreferred, then at least the structure of the tinned surface is modifiedas a result of the melting. In this case too, the soldering may beinspected optically through the said cutout. Such a deposit of solderingfiller metal in the form of a layer is produced with a thickness of afew microns (10 to 15 μm).

It is also possible to furthermore deposit coatings of soldering fillermetal, in the form of a thin layer of metal or in the form of droplets,on the contact surface itself, preferably around the cutout or cutouts.

As another advantage of said cutout or cutouts in the soldering regionof the contact surface, it has been found that a higher mechanicalstrength is also provided at the location of the actual soldering, insuch a way that the connection piece can withstand higher tensileforces. This is an advantage when continuing to handle such a pane,while it is being transported and fitted, because it is rare forconnection pieces to be soldered, that have been inadvertently broken,to be able to be repaired or, depending on the case, the pane inquestion must be extracted from the series.

Where appropriate, and as described in the abovementioned documentDE-C2-19 536 131, it is possible to provide several contact surfaceselectrically separated from one another and placed beside one another,each of which will be provided with at least one cutout (forinspection).

It is obvious that panes thus equipped are not just suitable as vehiclewindow panes. In the building field, there also exist many applicationsfor panes provided with electrical functional elements that have to beprovided with soldered contacts (for example, glazing fitted with analarm, surface heating, etc.).

Other details and advantages of the subject of the invention will becomeapparent from the figures of an illustrative example and from itsdetailed description that follows.

In the figures, which have been simplified and not drawn to scale:

FIG. 1 shows a schematic cross section through the components of acomposite glazing panel provided with a contact surface having a cutoutand a connection piece to be soldered before the composite panel isassembled; and

FIG. 2 shows, in cross section, the composite glazing panel afterassembly and the soldering of the location of the connection piece.

FIG. 1 shows an exploded representation of the border region of acomposite glazing panel 1, essentially formed from a first rigid pane1.1, a second rigid pane 1.2 and a thermoplastic and adhesive interlayer1.3. The two rigid panes are preferably made of glass, but they may,however, also be made of synthetic material. The interlayer is, forexample, a sheet of polyvinyl butyral—the usual adhesive material forcomposite glazing panels.

A thin-film system 2, highly transparent for visible light and capableof being thermally stressed, is applied to that plane surface of therigid pane 1.1 which faces the interlayer. It comprises at least oneelectrically conducting functional layer, preferably made of metal, andantireflection layers that contain, between them, said functional layer.The more detailed structure of the multilayer system is not essential asregards the invention in question here, so that it will not be explainedfurther.

Moreover, in addition to its thermal insulation action, or, depending onthe case IR reflection action, the electrically conducting layer of themultilayer system 2 will also be used in a manner known per se as aheating layer. Where appropriate, an antenna function may also be addedthereto. For this purpose, several external contacts have to beproduced.

We will now describe the structure of an individual connection piece. Inthe multilayer system 2, near the edge of the first rigid pane 1.1, acontact surface 3 is formed in a known manner from an electricallyconducting and nontransparent paste to be baked. It is interrupted by acutout 3A which, according to the invention, forms an observation windowin the middle of the contact surface 3.

The electrically conducting material of the contact surface 3 providesan electrically conducting connection with the electrically conductinglayer of the multilayer system 2. This connection is formed, forexample, by heating the pane 1.1 up to its softening temperature (about650° C.), where appropriate bending it, after having applied themultilayer system 2 and having printed the contact surface 3, and thenby leaving the pane to cool down. During this baking operation, thenecessary electrical contact is produced.

Experiments have shown that, in particular in other configurations ofthe multilayer system and/or of the contact surface material, it ispossible to use substantially lower temperatures, for example thetemperature for drying the screen-printing paste, of about 180° C., toproduce the electrical contact. This is a temperature range that isquite able to be withstood, for example, even by certain syntheticmaterials from which the transparent pane may be produced.

Unlike what has been shown, the multilayer system could also, again in amanner known per se, be applied only after application of the contactsurface; in this case, the multilayer system would cover the contactsurface in addition to the cutout. Electrical contacting is then alsoensured because the micro-irregularities in the contact surface passthrough the extremely thin multilayer system (thickness in the nanometerrange).

In general, the conductor structure shown here as a contact surface 3 isusually a rail, called a collector, that extends parallel to the edge ofthe pane 1.1 and practically over its entire length, and which makes itpossible for a current to be supplied into the layer 2 or, as the casemay be, extracted regularly therefrom. Depending on the function,several connection pieces to be soldered may also be provided on such acollector rail.

Above the cutout 3A is the end of a connection piece 4 to be soldered,which must be extended laterally outside the composite and which in thiscase is configured as a flat conductor with a support sheet 4.1 made ofsynthetic material and, at least, a metal foil conductor 4.2. A thinlayer 5 of soft solder filler metal is applied locally to the latter,within the limits of the actual soldering region. It forms the depositof soldering filler metal for soldering the connection piece 4 to besoldered to the contact surface 3. As a general rule, the size of thesurface to be soldered is between 100 and 400 mm². This also allowsrelatively high heater currents to be safely transferred.

Finally, an opaque border band 6 made of nontransparent paste to bebaked is formed on that side of the surface of the other rigid pane 1.2facing the interlayer 1.3. When the composite glazing panel is in itsfinal state (FIG. 2), it optically masks a soldering location, ordepending on the case the contact surface 3, to the outside.

FIG. 2 is a sectional view of the components shown in FIG. 1 afterassembly and connection of the layers or, depending on the case, thepanes of the composite glazing panel 1 and the production of theconnection piece to be soldered. It may also be seen that the meltingand the compression of the interlayer 1.3 along the edge of the paneseal the surfaces located further toward the inside. The connectionpiece 4 to be soldered extends toward the outside from the solderinglocation and is surrounded on all sides in an impermeable manner by thematerial of the interlayer. If necessary, the region located between theunderside of the connection piece 4 to be soldered and the surface ofthe pane may also be sealed using an appropriate sealant and/oradhesive. It will be recalled here that highly simplified representationhas been chosen.

It may be seen, in cross section, that the soft solder filler metal ofthe thin layer 5 has melted, for example by induction heating, and that,by the pressure that acts inside the composite glazing panel, it hasflowed right into the cutout 3A. The soldering filler metal must in thiscase not come into contact with the surface of the multilayer system 2.The amount of soldering filler metal of the soldering filler metaldeposit will be determined in such a way that the desired soldering areais obtained in a precise and reliable manner. This result of thesoldering, namely the modification of the soldering filler metal layer,can be detected without any problem with the naked eye through the pane1.1 and, as indicated, because the rigid pane 1.1 and the multilayersystem 2 are transparent. Contact between a soldering filler metal andthe side walls of the cutout result at the same time in major adhesionof the soldering filler metal to the material of the contact surface.

Although the embodiment described above can be used particularlyadvantageously on composite glazing panels that have the configurationindicated, it is not excluded to provide a cutout of the type and withthe functions that have been explained here also in contact surfaces tobe soldered on the monolithic panes.

1-10. (canceled)
 11. A transparent pane comprising: at least oneelectroconducting, non-transparent contact surface placed on one ofsurfaces of the pane, to connect it by soldering to a connection piece,wherein, in a region of the soldering location, the contact surface hasat least one cutout via which the soldering filler metal is visiblethrough the pane after the connection piece has been soldered to thecontact surface.
 12. The pane as claimed in claim 11, wherein, on thesurface of the pane, plural contact surfaces and/or plural cutouts areprovided in each contact surface.
 13. The pane as claimed in claim 11,wherein the soldering filler metal, after soldering, is spread over thecontact surface, and in the at least one cutout.
 14. The pane as claimedin claim 11, wherein the connection piece is provided, before soldering,with deposits of soldering filler metal that are present in a form ofdroplets or of a thin layer.
 15. The pane as claimed in claim 11,wherein the contact surface is provided, before soldering, around the atleast one cutout, with deposits of soldering filler metal that arepresent in a form of droplets or of a thin layer.
 16. The pane asclaimed in claim 11, wherein a multilayer system transparent to visiblelight is applied between the surface of the pane and the contact surfaceor on top of the contact surface provided with the cutout, whichmultilayer system comprises at least one electrically conducting layerthat is connected in an electrically conducting manner to the contactsurface.
 17. The pane as claimed in claim 16, wherein the multilayersystem is used as a surface heater and has an electrical contact. 18.The pane as claimed in claim 16, wherein the multilayer system is usedas an antenna and has an electrical contact.
 19. The pane as claimed inclaim 11, incorporated as a rigid pane in a composite glazing panel, atleast the contact surface and the soldering location both being locatedon an inside of the composite glazing panel.
 20. A composite glazingpanel having a first rigid pane as claimed in claim 11, and at least asecond rigid pane, wherein the second rigid pane is provided with anopaque coating that covers the contact surface and optically masks thecontact surface.